Method of plugging a water-producing formation

ABSTRACT

A method for selectively plugging a wellbore which produces both a hydrocarbonaceous material and water wherein a substantially gaseous material containing water vapor is injected into the wellbore and there is additionally injected a cementitious material which will not set up until reaching the producing formation or formations of the wellbore, the cementitious material being injected in amounts sufficient to substantially plug the portion or portions of the wellbore by which the water enters.

United States Patent Larry E. Knight Bakersfield, Calit;

Clyde W. Perry, Kern City, Tex. 61,87 2f Augf7, 1970 Nov. 2, 1971 Atlantic Richfield Company New York, N.Y.

Inventors Appl. No. Filed Patented Assignee METHOD OF PLUGGING A WATER-PRODUCING FORMATION 10 Claims, 4 Drawing Figs.

US. Cl 166/288, 166/292, 1 66/3103 Int. Cl ..E21 l133/l3,

E2lb 43724 Field of Search 166/285,

w13,616,ss6

[56] References Cited UNITED STATES PATENTS 1,026,589 5/1912 Jackson 166/288 X 1,379,657 5/1921 Swan 166/288 3,288,230 11/1966 Braunlich et a1. 166/292 3,369,603 2/1968 Trantham 166/288 X 3,373,814 3/1968 Eilers et al. 166/288 Primary Examiner- Ian A. Calvert Attorneys-Blucher S. Tharp and Roderick W. MacDonald ABSTRACT: A method for selectively plugging a wellbore which produces both a hydrocarbonaceous material and water wherein a substantially gaseous material containing water vapor is injected into the wellbore and there is additionally injected a cementitious material which will not set up until reaching the producing formation or formations of the wellbore, the cementitious material being injected in amounts sufficient to substantially plug the portion or portions of the wellbore by which the water enters.

STEAM PATENTEDHUV 2 WI 4| CEMENT INVENTORS LARRY E. KNIGHT CLYDE w. PERRY W WWW ATTORNEY METHOD OF PLUGGING A WATER-PRODUCING FORMATION BACKGROUND OF THE INVENTION After a wellbore has been drilled and is producing a hydrocarbonaceous material such as crude oil, water is sometimes also produced along with the oil so that a mixture of oil and water is actually produced from the wellbore at the earth's surface.

It is desirable, from both an economic viewpoint and from an optimization of oil production, to reduce the water production rate as much as possible. Generally, since the oil is hydrophobic and lighter than water, the water enters the wellbore at or near the bottom of the oil producing formation.

Heretofore the entry of this water into the wellbore has been prevented by filling the wellbore with cement by use of a dump-bailer technique hereinafter described in detail so that the top of the cement in the wellbore is above that portion of the producing formation by which the water enters the wellbore. In this manner the bottom portion of the producing formation and the water entering the wellbore from this formation are cut off from the wellbore and substantially only oil enters the wellbore from the remainder of the formation which is not cut off by this cement plug.

The dump-bailing process is an expensive and time-consuming process because it involves dumping separate batches of cement on the bottom of the wellbore until the desired height of cement is built up.

Also, if water should be entering the wellbore from points near the top of the producing formation, the dump-bailer technique cannot shut off this flow of water without substantially completely stopping the production of oil from the producing formation as well.

Further, if there is a plurality of producing formation vertically spaced from one another along the length of the wellbore, the higher producing formation or formations can not be plugged in this manner without cutting off all communication of the wellbore with the lower producing formation or formations.

It is therefore very desirable from both an economic and operating point of view to be able to selectively plug a portion or portions of one or more producing formations in a wellbore by which water is entering that wellbore without cutting off communication of the wellbore to the remainder of the formation or formations that are producing oil into the wellbore.

SUMMARY OF THE INVENTION According to this invention there is provided a method for selectively plugging a wellbore as to those portions of a formation or formations by which water enters the wellbore. The selective plugging is accomplished without plugging the remainder of the formation or formations which are producing a substantially liquid hydrocarbonaceous material which is more viscous than water.

By this invention the portion of the formation through which water passes into the wellbore can be selectively plugged by injection into the wellbore can substantially gaseous material containing water vapor and additionally injecting a cementitious material which will not set up at least until it has reached the producing formation, the cementitious material being injected in amounts sufficient to substantially plug the water-producing portion of the wellbore by which the water enters.

Since the gaseous material carries the cementitious material and since the gaseous material will follow the path of least resistance in passing into a formation, it will preferentially pass into those portions of the producing formation through which water is passing. This is so because the water is less viscous than the hydrocarbonaceous material. Thus, the gaseous material carrying the cementitious material will preferentially enter those portions of a formation through which water is passing as opposed to the remaining portions of the formation through which the hydrocarbonaceous material is passing.

By the method of this invention the dump-bailer technique is avoided, cementitious material is injected into the wellbore as needed, and the cementitious material is deposited on and/or in the formation substantially only at the points where water is passing without hindering the remaining portions of the formation and regardless of whether the water-passing points of the formation are at the top, middle, or bottom of a formation.

By the method of this invention selective plugging of waterproducing portions of a formation is obtained throughout the length of a formation in a shorter time and at less expense than the dump-ballet technique. Also, a plurality of formations in a wellbore can be selectively plugged at the same time.

Further, since the cement plug from the dump-bailer technique normally extends beyond the water producing portion of the formation, it inherently plugs off a portion of the formation that remains. This overlapping of the cement plug into the oil-producing portion of the formation is also minimized by the method of this invention.

Accordingly, it is an object of this invention to provide a new and improved method for selectively plugging at least one portion of a wellbore. It is another object to provide a new and improved method for producing a substantially hydrocarbonaceous material from a wellbore wherein the hydrocarbonaceous material is more viscous than water and wherein water enters the wellbore with the hydrocarbonaceous material, the entry of water into the wellbore being substantially stopped without substantial interference with the entry of the hydrocarbonaceous material into the wellbore. It is another object to provide a new and improved method for plugging one or more portions of one or more producing formations through which water is passing and without interfering with the production of hydrocarbonaceous material into the wellbore, this selective plugging being achieved in a continuous manner and, if necessary, also being achieved in a continuous manner and, if necessary, also being achieved at a plurality of places vertically spaced from one another in the wellbore at substantially the same time.

Other aspects, objects, and advantages of this invention will be apparent to those skilled in the art from this disclosure and the appended claims.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows a cross-sectional view of a wellbore through a producing formation and a simplified version of the wellhead at the top of the wellbore.

FIGS. 2 and 3 show the bottom portion of the wellbore of FIG. 1 when plugged in accordance with the dump-bailer technique.

FIG. 4 shows the bottom portion of the wellbore of FIG. 1 when plugged in accordance with the method of this invention.

More specifically, FIG. 1 shows the earth 1 having a wellbore 2 which passes through a producing formation 3 and terminates in the earth at 4.

wellbore 2 is completed at the earth's surface with wellhead 5 which has various conduit means 6 through 8 for obtaining entry into the wellbore. For sake of clarity other conventional wellhead equipment is not shown.

Producing formation 3, for sake of example, produces a substantially liquid hydrocarbonaceous material from an upper portion 10 as shown by arrows l1 and water from a lower portion 12 as shown by arrows 13. A mixture of hydrocarbonaceous material and water collects in a pool 14 on bottom 4 of wellbore 2.

A conventional pumping device well known in the art can be inserted into the wellbore by way of conduit 7 and into pool 14 to pump the mixture of oil and water to the earth s surface.

As mentioned above, however, it is desirable to prevent the entry of water from portion 12 into the wellbore so that all that collects in pool M is hydrocarbonaceous material from portion 10. In this manner only the more valuable hydrocarbonaceous material is pumped to the earths surface and separation of the hydrocarbonaceous material from the water at the earths surface is eliminated.

The prior art solution for such a problem was the dumpbailer technique wherein, as shown in FIG. 2, a dump-bailer 20 such as that shown in U.S. Pat. No. 2,956,624 is lowered by a wire line 21 passing through conduit 7 of FIG. 1. Dumpbailer 20 contains a single batch of cement therein and carries this batch to the bottom of the wellbore where the cement 22 is dumped on bottom 4. Dump-bailer 20 is then elevated to the earth's surface, filled with another batch of cement, lowered again to the bottom of the wellbore, and its contents dumped. This sequence of steps is repeated a number of times until the wellbore is filled with cement above portion 12 into portion as shown in FIG. 3. In this manner pool M collects on top of cement 22 and since portion 12 is plugged, substantially only hydrocarbonaceous material passes from formation 3 into the wellbore as shown by arrows 30.

It can clearly be seen from FIGS. 2 and 3 that it is time consuming and expensive to raise and lower dump-bailer 20 a number of times until the cumulative number of batches of cement dumped are sufiicient to create the cement plug of FIG. 3. It can further be seen that the cement plug of FIG. 3 cannot be used to plug an upper portion of the wellbore to prevent the entry of water from that portion because, in effect, the entire producing fonnation would then be plugged. Further, it can be seen that the cement plug of FIG. 3 overlaps portion 12 into portion 10 and thereby plus part of the hydrocarbonaceousproducing portion 10. This overlapping reduces the hydrocarbon production capability of the well.

By the method of this invention a substantially gaseous material containing sufficient water vapor to wet any cement added thereto, e.g., at least about 20 volume percent water vapor based on the total volume of the gaseous material, is injected into the wellbore. This is shown in FIG. 1 by way of arrow 40 injecting steam into conduit 8. Although steam is presently preferred as a gaseous material, substantially any carrier gas can be used if it has sufficient water vapor to prevent drying out of cement added thereto so that the cement will not agglomerate into balls and simply fall to bottom 4 of the wellbore. For example, air, carbon dioxide, natural gas, and the like can be employed if sufficiently humid.

There is additionally injected by way of conduit 6 as shown by arrow 41 a cementitious material which is to be carried by steam 40 down the wellbore. The cementitious material can be cement alone or cement with additional additives such as conventional promoters and/or retarders in amounts such that the cement will not set up or otherwise harden as it passes down the wellbore and at least until it has reached formation 3. The cementitious material is added in amounts sufficient to substantially plug portion 12 by passing into portion 12 as shown by 42 and/or by forming a layer over portion 12 as shown by 43.

Pool 14 still collects on the bottom 4 of wellbore 12 as shown in FIG. 1 except that the water-producing portion 12 of formation 3 is plugged. Portion 12 would be plugged whether that portion was at the bottom, in the middle, or at the top of formation 3. Also, substantially only the water-producing area 12 is plugged without any substantial overlap of the cement onto hydrocarbonaceous-producing portion 10.

The same results as shown in FIG. 4 can be achieved in a plurality of producing fonnations along the vertical length of wellbore 2 and above and/or below formation 3. Thus, plugging of one or more water-producing portions of one or more vertically separated formations can be achieved at the same time.

The amount of cementitious material injected will vary widely depending upon the number of formations present and the number of portions of each formation to be plugged. It will generally be at least about l0 pounds of cementitious material injected per wellbore. Cementitious material injected can be substantially any conventional oil-well-cementing composition. A suitable composition would be a steam curable cement such as that disclosed in U.S. Pat. No. 3,447,937. It can also be desirable to add sand to the cementitious material in order to make the cement deposited in the wellbore more resistant to decomposition upon subsequent exposure to steam and similar heated fluids.

Since the hydrocarbonaceous material produced from formation 3 is relatively viscous in that it is at least more viscous than water, it can be desirable, after the addition of cementitious material to the wellbore is terminated, to continue the injection into the wellbore of a heated fluid. The fluid should be at a temperature sufficiently elevated to help reduce the viscosity of the hydrocarbonaceous material in formation 3 thereby facilitating the low of this material from formation 3 into pool 14. In the case shown in FIGS. 1 and 4, this can readily be achieved by simply continuing the injection of steam 40 after termination of injection of cement-gas mixture 41. However, if the particular gaseous steam employed is not one which is heated, then termination of injection of this steam 40 at the same time as termination of injection of cement d1 can be achieved followed by initiation of injection of a heated fluid such as steam.

EXAMPLE The method of this invention is carried out in a well having substantially the structure of that shown in FIG. 1. Steam at a temperature of 300is injected into the wellbore at a rate of 6,000 pounds lhour. During injection, a cementitious composition is injected into the wellbore at varying rates of onehalf gallon/minute to 10 gallons/minute. The cementitious composition is composed of 99 pounds of Class C cement (fully and completely disclosed as to its composition and properties in American Petroleum Institute publication RP 10 A, l3th edition, Jan. l967) and 56 pounds of minus ZOO-mesh silica flour mixed with one cubic foot of water. In all, 5,000 to 1,500 pounds of the cementitious material is injected over a period of 8 hours.

Thereafter the introduction of cementitious material is terminated and the steam injection continued for 5 to 10 days. The steam injection is then terminated and the wellbore pumped. The percent of water pumped from the wellbore is substantially reduced thereby indicating that the leakage from the water zone into the wellbore has been substantially stopped.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a method for selectively plugging a wellbore producing a substantially liquid hydrocarbonaceous material wherein said hydrocarbonaceous material is more viscous than water and wherein water enters the wellbore along with said hydrocarbonaceous material, the improvement comprising injecting into said wellbore a substantially gaseous material containing sufficient water vapor to wet any cement added thereto, additionally injecting a cementitious material to be carried by said gaseous material and which will not set up at least until it has reached the producing fonnation or formstions of said wellbore, said cementitious material being injected in amounts sufficient to substantially plug the portion or portions of the wellbore by which the water enters.

2. A method according to claim 1 wherein after said injection of cementitious material a heated fluid is injected into said wellbore, said heated fluid being at a temperature suffieiently elevated to help reduce the viscosity of said hydrocarbonaceous material.

3. A method according to claim 2 wherein said cementitious material sets up when exposed to said heated fluid.

4. A method according to claim 2 wherein said heated fluid is steam.

5. A method according to claim 1 wherein said substantially gaseous material is steam.

6. A method according to claim 1 wherein said substantially gaseous material contains at least 20 volume percent water vapor based on the total volume of said gaseous material.

7. A method according to claim 1 wherein said cementitious material contains at least one promoter or at least one retarder or a combination thereof to adjust the set up time for the cement so that it will not set up before being carried to and/or into the formation or formations by which water enters the wellbore.

8. A method according to claim 1 wherein claim 1 wherein said hydrocarbonaceous material is viscous crude petroleum liquid, said gaseous material is steam, cement is added to said steam in an amount of at least pounds and while said steam is being injected into the wellbore, and after the addition of said cement is terminated injection of said steam is continued for a time sufficient to help reduce the viscosity of said crude petroleum.

9. A method according to claim 8 wherein said cement has added thereto at least one retarder in an amount sufficient to keep the cement from setting up before reaching the formation or formations through which water enters the wellbore.

10. A method according to claim 9 wherein said cement also has added thereto silica flour in an amount sufficient to keep the cement from decomposing due to continued exposure to steam after it has set up in the wellbore. 

2. A method according to claim 1 wherein after said injection of cementitious material a heated fluid is injected into said wellbore, said heated fluid being at a temperature sufficiently elevated to help reduce the viscosity of said hydrocarbonaceous material.
 3. A method according to claim 2 wherein said cementitious material sets up when exposed to said heated fluid.
 4. A method according to claim 2 wherein said heated fluid is steam.
 5. A method according to claim 1 wherein said substantially gaseous material is steam.
 6. A method according to claim 1 wherein said substantially gaseous material contains at least 20 volume percent water vapor based on the total volume of said gaseous material.
 7. A method according to claim 1 wherein said cementitious material contains at least one promoter or at least one retarder or a combination thereof to adjust the set up time for the cement so that it will not set up before being carried to and/or into the formation or formations by which water enters the wellbore.
 8. A method according to claim 1 wherein claim 1 wherein said hydrocarbonaceous material is viscous crude petroleum liquid, said gaseous material is steam, cement is added to said steam in an amount of at least 10 pounds and while said steam is being injected into the wellbore, and after the addition of said cement is terminated injection of said steam is continued for a time sufficient to help reduce the viscosity of said crude petroleum.
 9. A method according to claim 8 wherein said cement has added thereto at least one retarder in an amount sufficient to keep the cement from setting up before reaching the formation or formations through which water enters the wellbore.
 10. A method according to claim 9 wherein said cement also has added thereto silica flour in an amount sufficient to keep the cement from decomposing due to continued exposure to steam after it has set up in the wellbore. 